This invention relates to electromagnetic radiation shields and more particularly, to an electromagnetic radiation shielding device particularly suitable for shielding flat cable. The shielding device of the present invention provides novel means for making good electrical connection to it and may be used as a floating ground or can be easily connected to a common system ground.
Current carrying cables often require an insulating shield effective to prevent electromagnetic energy radiation therefrom or from effecting same. As electrons move from one place to another, a field of electromagnetic energy is created which radiates outwardly from the point of generation. This electromagnetic energy influences the electrons in any conducting material within its field. It is important, therefore, to be able to contain the electromagnetic field within its source, and to prevent spurious electromagnetic energy from affecting other systems by permeating normal electrical insulation. Shielding of electromagnetic energy radiation may be accomplished by enclosing the current carrying cable within a continuously conductive shield. It is desirable that the shield not have breaks or discontinuities through which electromagnetic energy can leak since this would result in the loss of shielding effectiveness.
A suitable shielding device for current carrying cable which is flat cable must be of sufficient dimensions to enable the flat cable to be inserted into it. It is desirable that a shielding device for such flat cable, even though providing a continuously conductive enclosure of adequate strength along the length of the flat cable, nevertheless be lightweight and flexible. Since many applications require the use of current carrying flat cable having a given degree of flexibility, the flat cable shielding device should likewise have sufficient flexibility to enable its use in such applications. Accordingly, a flat cable shielding device should be as lightweight and as flexible as possible to enable its use in a broad range of applications. The shielding device must however, also have sufficient strength to withstand the demands or ordinary use.
While a flat cable shielding device could be formed integrally with the cable, it is desirable that the shielding device be distinct from the flat cable itself. In this manner, the shielding device can be used only where necessary and can be employed in conjunction with flat cables having differing dimensions.
The shielding device itself must often be insulated so as to be electrically isolated from its environment. Nevertheless, it is desirable to provide a flat cable shielding device which can be used as a floating ground or which can be grounded to a common system ground. Therefore, it is desirable that the shielding device be electrically insulated and yet provide a means by which electrical connections can easily be made to it. With respect to a shielding device for flat cable, it is desirable to make good positive electrical connections to the shielding device without adversely affecting the effectiveness of the shielding of electromagnetic energy and without damaging or otherwise interfering with the current carrying flat cable. It is an important feature of the flat cable shielding device of the present invention that it provides means for easily making good electrical connections to it without significantly adversely affecting its effectiveness and without interfering with the flat cable within it.
An additional significant problem is seen to exist in the degree of difficulty encountered when inserting the current carrying cable into the shielding device. This problem is seen to be especially acute with respect to shielding devices for flat cable. Where the shielding device is potentially of great length and since it is preferrably flexible and may necessarily become dilated an/or curved or uncurved during the insertion of the flat cable, it may require considerable force to insert the flat cable into the shielding device. However, the flat cable, especially for example, if it is wide and thin cable, may be unable to transmit sufficient force to the leading edge. Rather, it may buckle or bend.
Accordingly, it is an object of the present invention to provide a flat cable shielding device into which flat cable may be easily inserted. Even, for example, flat cable which is wide and thin may be easily inserted into the flat cable shielding device of the present invention.
Another object of the present invention is to provide a flat cable shielding device which provides means for easily making good electrical connections without significantly adversely affecting the effectiveness of the shielding of electromagnetic energy and without interfering with or damaging the current carrying flat cable.
Another object of the present invention is to provide a flat cable shielding device which can be easily and used as a floating ground on which can be easily grounded to a common system ground. Another objective of the present invention is to provide a flat cable shielding device which is electrically insulated from its environment but to which good electrical connections can easily be made.
Another object of the present invention is to provide a flat cable shielding device providing a continuously conductive enclosure along the length of the flat cable. It is a further object of the present invention to provide such a shielding device which is also lightweight and flexible. It is a further object to provide such a shielding device which also ha sufficient strength to withstand the demands of ordinary use.
These and other objects are achieved in accordance with the following description of the present invention.